The specific objective of this work will be to clearly elucidate the essential genetic characteristics and the exact biomolecular interactions which give a microorganism the ability to survive in the oral cavity and induce dental caries. This will be accomplished by: a. isolating mutants of "caries-inducing" and noncariogenic oral streptococci. b. characterizing the mutants by determining the enzyme activity which has been altered. c. testing the ability of the mutants to cause plaque formation and dental caries in hamsters. Additional work will involve studies designed to clarify the basic physico-chemical mechanisms involved in the formation of dental caries. This will be accomplished by: a. comparing the glucans produced by wild-type and mutant streptococci. b. comparing the exoenzymes produced by cariogenic bacteria. c. evaluating the role of various bacterial components and products on isotypic and heterotypic cell-cell adhesion and cell-oral surface adherence.